Physiological Disorder

Dr. Sanjeev Kumar

Assistant Professor/Scientist Plant Pathology JNKVV-Jabalpur

[email protected]

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INTRODUCTION

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1. Plants grow best within certain ranges of the various abiotic factors that make up their environment. 2. Such factors include temperature, soil moisture, soil nutrients, light, air, soil pollutants, air humidity, soil structure and pH. 3. Although these factors affect cultivated plants, which are often grown in areas that are at the margins and beyond their normal habitat 4. Therefore, that barely meet the requirements for normal growth.

General Characteristics

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1. Abiotic, i.e., noninfectious diseases of plants, is that they are caused by the lack or excess of something that supports life. 2. Occur in the absence of pathogens and cannot, therefore, be transmitted from diseased to healthy plants. 3. May affect plants in all stages of their lives (e.g., seed, seedling, mature plant, or fruit), and they may cause damage in the field, in storage, or at the market. 4. Symptoms caused by noninfectious diseases vary in kind and severity with the particular environmental factor involved and with the degree of deviation of this factor from its normal. 5. Symptoms may range from slight to severe, and affected plants may even die.

Diagnosis

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1. Diagnosis of noninfectious diseases is sometimes made easy by the presence of characteristic symptoms known to be caused by the lack or excess of a particular factor on the plant . 2. At other times, diagnosis can be arrived at by carefully examining and analyzing several factors: • Weather conditions prevailing before and during the appearance of the disease. • Recent changes in the atmospheric and soil contaminants at or near the area where the plants are growing. • Cultural practices, or possible accidents in the course of these practices, preceding the appearance of the disease.

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3. Symptoms of several noninfectious diseases are too indistinct and closely resemble those caused by several viruses, mollicutes, and many root pathogens. Diagnosis of such noninfectious disease then becomes a great deal more complicated. 1. One must obtain proof of absence from the plant of any of the pathogens that could cause the disease. 2. One must reproduce the disease on healthy plants after subjecting them to conditions similar to those thought of as the cause of the disease. 3. To distinguish further among environmental factors causing similar symptoms, the investigator must cure the diseased plants. 4. if possible, by growing them under conditions in which the degree or the amount of the suspected environmental factor involved has been adjusted to normal.

TEMPERATURE EFFECTS

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1. Plants normally grow at a temperature range from 1 to 40°C. 2. Most kinds of plants growing best between 15 and 30°C. 3. Perennial plants and dormant organs (e.g., seeds and corms) of annual plants may survive temperatures considerably below or above the normal temperature range of 1 to 40°C. 4. Young, growing tissues of most plants, however, and the entire growth of many annual plants are usually quite sensitive to temperatures near or beyond the extremes of this range. 5. A plant may also differ in its ability to withstand extremes in temperature at different stages of its growth. 6. Thus, older, hardened plants are more resistant to low temperatures than young seedlings.

Various Types of Symptoms due to Environment factors

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High-Temperature Effects

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1. Plants are generally injured faster and to a greater extent when temperatures become higher than the maximum for growth than when they are lower than the minimum. 2. High temperature seems to cause its effects on the plant in conjunction with the effects of other environmental factors, particularly excessive light, drought, lack of oxygen, or high winds accompanied by low relative humidity. 3. High temperatures are usually responsible for SUNSCALD INJURIES

SUNSCALD INJURIES

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• Appearing on the Sun-exposed sides of fleshy fruits and vegetables. • Peppers, apples, tomatoes, onion bulbs, and potato tubers. • On hot, sunny days the temperature of the fruit tissues beneath the surface facing the sun may be much higher than that of those on the shaded side and of the surrounding air. • This results in discoloration, a water-soaked appearance, blistering, and desiccation of the tissues beneath the skin, which leads to sunken areas on the fruit surface. 4. Too high a soil temperature at the soil line sometimes kills young seedlings or causes cankers at the crown on the stems of older plants . 5. High tempertures also seem to be involved in the water core disorder of apples and, in combination with reduced oxygen, in the blackheart of potatoes.

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Low-Temperature Effects

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1. Far greater damage to crops is caused by low than by high temperatures. 2. They may also cause excessive sweetening and, on frying, undesirable caramelization of potatoes due to the hydrolysis of starch to sugars at the low temperatures. 3. Temperatures below freezing cause a variety of injuries to plants. Such injuries include • Damage caused by late frosts to young leaves and meristematic tips • Damage of ntire herbaceous plants • Frost killing of buds of peach, cherry, and other trees,. • Killing of flowers, young fruit, and, sometimes, succulent twigs of most trees.

Low-Temperature Effects

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4. Fleshy tissues, such as tomato fruit, canola pods, and

5.

6. • •

potato tubers, may be injured at subfreezing temperatures . In potatoes, the injury varies depending on the degree of temperature drop and the duration of the low temperature. Early injury affects only the main vascular tissues and appears as A ring-like necrosis Injury of the finer vascular elements that are interspersed in the tuber gives the appearance of netlike necrosis.

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Mechanisms of Low- and High-Temperature Injury to Plants

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1. High temperatures • Apparently inactivate certain enzyme systems and accelerate others, thus leading to abnormal biochemical reactions and cell death. • Cause coagulation and denaturation of proteins, disruption of cytoplasmic membranes, suffocation, and possibly release of toxic products into the cell. II. Low temperatures 1. Injure plants primarily by inducing ice formation between or within the cells. 2. when the intercellular water becomes ice, more vapor (water) moves out of the cells and into the intercellular spaces, where it also becomes ice. 3. The reduced water content of the cells depresses further the freezing point of the intracellular water. 4. Ice crystals form within the cell, disrupt the plasma membrane,

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5. Ice formation in super cooled water within leaves is influenced greatly by the kinds and numbers of epiphytic bacteria that may be present on the leaves. 6. Certain strains of some pathogenic (e.g., Pseudomonas syringae) bacteria and of some saprophytic bacteria, when present on or in the substomatal cavities of leaves, act as catalysts for ice nucleation. 7. By their presence alone, such ice nucleation-active bacteria induce the supercooled water around them and in the leaf cells to form crystals, thereby causing frost injury to the leaves, blossoms, and so on at temperatures considerably higher (-1°C) than would have happened in the absence of such bacteria (approximately -5 to -10°C). 8. This loss causes plasmolysis and dehydration of the protoplasm, which may cause coagulation.

MOISTURE EFFECTS Low Soil Moisture Effects

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1. Moisture disturbances in the soil are probably responsible for more plants growing poorly and being unproductive annually, over large areas, than any other single environmental factor. 2. Small or large territories may suffer from drought over time. 3. The subnormal amounts of water available to plants in these areas may result in reduced growth, a diseased appearance, or even death of the plants. 4. Lack of moisture may result in patches of diseased looking plants, while the immediately surrounding areas appear to contain sufficient amounts of moisture and the plants in them grow normally. 5. Plants suffering from lack of sufficient soil moisture usually remain stunted, are pale green to light yellow, have few, small and drooping leaves, flower and fruit sparingly, and, if the drought continues, wilt and die . 6. Annual plants are considerably more susceptible to short periods of insufficient moisture. 7. Even perennial plants and trees are damaged by prolonged periods of drought and produce less growth, small, scorched leaves and short twigs, dieback, defoliation, and finally wilting and death. 8. Plants weakened by drought are also more susceptible to certain pathogens and insects.

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Low Relative Humidity Effects

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1. Lack of moisture in the atmosphere, i.e., low relative humidity, is usually temporary and seldom causes damage. 2. When combined with high wind velocity and high temperature, however, it may lead to excessive loss of water from the foliage. 3. It may result in leaf scorching or burning, shriveled fruit, and temporary or permanent wilting of plants. 4. Conditions of low relative humidity are particularly common and injurious to house plants during the winter. 5. In modern homes and apartments, heating provides comfortable temperatures for plant growth, but it often dries the air to relative humidities of 15 to 25% which are equivalent to that of desert environments. 6. Potted plants kept under these conditions not only use up the water much faster, grow poorly, and may begin to wilt sooner, but the leaves, especially the lower ones, of many kinds of plants become spotted or scorched and fall prematurely, while their flowers suddenly wither and drop off. 7. These effects are particularly noticeable when plants are brought into such a hot, dry house directly from a cool, moist greenhouse or florist’s shop.

High Soil Moisture Effects

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1. Excessive soil moisture occurs much less often than drought where plants are grown. 2. Poor drainage or flooding of planted fields, gardens, or potted plants may result in more serious and quicker damage, or death, to plants than that from lack of moisture. 3. Poor drainage results in plants that lack vigor, wilt frequently, and have leaves that are pale green or yellowish green. 4. Flooding during the growth season may cause permanent wilting and death of succulent annuals within 2 to 3 days. 5. Excessive soil moisture caused by flooding or by poor drainage, the fibrous roots of plants decay, probably because of the reduced supply of oxygen to the roots. 6. Oxygen deprivation causes stress, asphyxiation, and collapse of many root cells. 7. Wet, anaerobic conditions favor the growth of anaerobic microorganisms that, during their life processes, form substances, such as nitrites, that are toxic to plants. • Common symptom of houseplants, and sometimes of outdoor plants. • Caused by excessive moisture is the so-called edema [or oedema (swelling)]. • Edema appears as numerous small bumps on the lower side of leaves or on stems.

EDEMA

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1. Common symptom of houseplants, and sometimes of outdoor plants,. 2. Caused by excessive moisture is the so-called edema [or oedema (swelling)]. 3. Appears as numerous small bumps on the lower side of leaves or on stems. 4. The “bumps” are small masses of cells that divide, expand, and break out of the normal leaf surface and at first form greenish- white swellings or galls. 5. Later, the exposed surface of the swelling becomes rusty colored and has a corky texture. 6. Edema is caused by overwatering, especially during cloudy, humid weather, and can be avoided by reduced watering and providing better lighting and air circulation to the plant. 7. Many other disorders are caused by excessive or irregular watering. 8. Example, that tomatoes and some other fruits, such as cherries and grapes, grown under rather low moisture conditions at the time they are ripening often crack if they are suddenly supplied with abundant moisture by overwatering or by a heavy rainfall. 9. Bitter pit of apples, consisting of small, sunken, blackspots on the fruit, is the result of an irregular supply of moisture, although excessive nitrogen and low calcium fertilization also seem to be involved in bitter pit

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INADEQUATE OXYGEN

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1. Low oxygen conditions in nature are generally associated with high soil moisture or high temperatures. 2. A combination of high soil moisture and high soil or air temperature causes root collapse in plants. 3. The first condition, apparently, reduces the amount of oxygen available to the roots, whereas the other increases the amount of oxygen required by the plants. 4. The two effects together result in an extreme lack of oxygen in the roots and cause their collapse and death. 5. Best known such case is the development of the so-called BLACKHEART OF POTATO • Fairly high temperatures stimulate respiration and abnormal enzymatic reactions in the potato tuber. • Oxygen supply to the cells in the interior of the tuber is insufficient to sustain the increased respiration and the cells die of suboxidation. • Enzymatic reactions activated by the high temperature and suboxidation go on before, during, and after the death of the cells. • These reactions abnormally oxidize normal plant constituents into dark melanin pigments. • The pigments spread into the surrounding tuber tissues and finally make them appear black.

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LIGHT

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1. LACK OF SUFFICIENT LIGHT • Retards chlorophyll formation and promotes slender growth with long internodes,. • Leading to pale green leaves, spindly growth, and premature drop of leaves and flowers. • This condition is known as ETIOLATION. • Etiolated plandoors only when plants are spaced too close together or when they are growing under trees or other objects. • Etiolation of various degrees, where plants often receive inadequate light. • Etiolated plants are usually thin and tall and are susceptible to lodging. II. EXCESS LIGHT • Rather rare in nature and seldom injures plants. • Many injuries attributed to light are probably the result of high temperatures accompanying high-light intensities. • Excessive light cause SUNSCALD OF PODS of beans grown at high altitudes • It is due to the absence of dust, more light of short wavelengths reaches the earth. • The pods develop small, water-soaked spots that quickly become brown or reddish brown and shrink.

Air Pollutants and Kinds of Injury to Plants

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NUTRITIONAL DEFICIENCIES IN PLANTS

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1. Plants require several mineral elements for normal growth. 2. Some elements, such as nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur, needed in relatively large amounts, are called MAJOR ELEMENTS, 3. Element such as iron, boron, manganese, zinc, copper, molybdenum, and chlorine, needed in very small amounts, are called trace or minor elements or MICRONUTRIENTS. 4. Both major and trace elements are essential to the plant. 5. When they are present in the plant in amounts smaller than the minimum levels required for normal plant growth, the plant becomes diseased and exhibits various external and internal symptoms. 6. The symptoms may appear on any or all organs of the plant, including leaves, stems, roots, flowers, fruits, and seeds.

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Nutritional Deficiencies or Disorder in Plants

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1. Deficiency of minerals viz, Nitrogen, Phosphorus, potash, manganese , zinc, copper , iron, magnesium, boron, , etc. results in disorders in plant metabolism and cause hunger signs in the crops 2. Excess and deficiency of minerals disturbs nutritional balance needed for good metabolism in the plant, hence hindering the effect of essential element. 3. Deficiencies and excess of minerals also reduce the resistance of plant to fungal, bacterial and other diseases. 4. Kind of symptoms produced by deficiency of a certain nutrient depend primarily on the functions of that particular element in the plant. 5. Nutrient mobility plays an important role in determining the site of the deficiency symptoms. 6. For highly mobile elements like nitrogen and potassium, the deficiency symptoms appear predominantly in older and mature leaves. 7. Deficiency of poorly mobile elements, like calcium, boron and iron show up in younger leaves. 8. The symptoms of deficiency of moderately mobile elements like

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Plant disease due to lack of minerals

Sr. No 1 2 3 4 5

Deficient Nutrient Nitrogen (N) Phosphorus (P) Potassium (K) Magnesium (Mg) Boron (B)

Disease Red leaf of cotton Dwarfening of cotton Cotton rust leaf spot of alfa alfa. Sand drown disease in tobacco Internal cork of apple Cracked stem of celery Black tip of mango Heart rot of sugarbeet Brown heart of cabbage and turnip Internal brown spot of sweet potato Terminal bud breakdown of tobacco Fruit pitting and dieback of olive Hollow stem of brassica

6

Copper (Cu)

Reclamation disease of oats Diebacks of citrus

Plant disease due to lack of minerals Sr.No 7

Deficient Nutrient Manganese( Mn)

Disease Pahala blight of Sugarcane Marsh spot of garden pea Grey speck of oats.

8

Zinc (Zn)

White bud of corn Little leaf of apple Bronzing of twigs Rosette of fruits trees Mottle leaf of citrus Khaira disease of rice

9 10 11

Iron (Fe) Molybdenum (Mo) Calcium(ca)

Green netting of citrus Whiptail disease of cauliflower. Blossom end rot of tomato Black heart of celery

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Boron Deficiency Symptoms

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Micronutrient Deficiency symptoms

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